Audi 100 dupa 1991 brake system

Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
Audi 100 1991 ➤
Brake system
Edition 04.1998
Service
Service Department. Technical Information

List of Workshop Manual Repair GroupsList of Workshop Manual
Repair GroupsList of Workshop Manual Repair Groups
Audi 100 1991 ➤
Brake system
Repair Group
00 - Technical data
45 - Anti-locking brake system
46 - Brakes, Brake mechanics
47 - Brakes, Brake hydraulics
Technical information should always be available to the foremen and mechanics, because their careful
and constant adherence to the instructions is essential to ensure vehicle road-worthiness and safety. In
addition, the normal basic safety precautions for working on motor vehicles must, as a matter of course,
be observed.
Service
All rights reserved.
No reproduction without prior agreement from publisher.
Copyright © 2010 Audi AG, Ingolstadt 00052505120

Contents
00 - Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1.1 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1.2 Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
45 - Anti-locking brake system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
1 Safety precautions and general servicing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
1.1 Safety precautions and general servicing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
1.2 High- and low pressure test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
2 Removing and installing components of ABS system on front axle . . . . . . . . . . . . . . . . . . . .4
2.1 Removing and installing components of ABS system on front axle . . . . . . . . . . . . . . . . . . . .4
2.2 Removing and installing speed sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.3 Checking rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
3 Removing and installing components of ABS system on rear axle, FWD models . . . . . . . .7
3.1 Removing and installing components of ABS system on rear axle, FWD models . . . . . . . .7
3.3 Checking rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
4 Removing and installing componpents of ABS system on rear axle, 4WD models . . . . . . . .12
4.1 Removing and installing componpents of ABS system on rear axle, 4WD models . . . . . . . .12
4.3 Checking rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
5 Anti-lock brake system (ABS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
5.1 Anti-lock brake system (ABS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
5.2 Hydraulic unit and brake pipes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
5.3 Removing and installing ABS control unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
6 Anti-lock brake system (ABS) with electronic differential lock . . . . . . . . . . . . . . . . . . . . . . . .21
6.1 Anti-lock brake system (ABS) with electronic differential lock . . . . . . . . . . . . . . . . . . . . . . . .21
7 Anti-lock brake system (ABS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
7.1 Anti-lock brake system (ABS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
7.2 ABS with electronic differential lock (ABS/EDL), ABS/EDL with traction control system (TCS)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
7.4 Removing and installing control unit for ABS/EDL or TCS . . . . . . . . . . . . . . . . . . . . . . . . . .30
8 Bosch 5.0 Anti-lock brake system (ABS) as of MY `95 (chassis no. 4ASN ...) . . . . . . . . . .31
8.1 Bosch 5.0 Anti-lock brake system (ABS) as of MY `95 (chassis no. 4ASN ...) . . . . . . . . . .31
8.2 ABS with electronic differential lock (ABS/EDL), ABS/EDL with traction control system (TCS)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
8.4 Removing and installing control unit for ABS/EDL or TCS . . . . . . . . . . . . . . . . . . . . . . . . . .39
46 - Brakes, Brake mechanics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
1 Servicing front brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
1.1 Servicing front brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
1.2 Servicing Teves/Ate front brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
1.3 Removing and installing brake pads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
1.4 Servicing front brake, internal caliper disc brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
1.6 Servicing front brakes, two-piston brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
2 Servicing rear wheel brake (disc brake) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
2.1 Servicing rear wheel brake (disc brake) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
Audi 100 1991 ➤
Brake system - Edition 04.1998
Contents i

2.3 Basic setting of rear wheel brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
2.4 Adjusting handbrake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
3 Servicing rear wheel brake (drum brake) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
3.1 Servicing rear wheel brake (drum brake) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
3.2 Removing and installing rear brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
3.3 Resetting brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
3.4 Servicing rear brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
3.5 Removing and installing brake shoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80
3.6 Adjusting handbrake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81
4 Handbrake lever - exploded view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82
4.1 Handbrake lever - exploded view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82
4.2 Removing and installing handbrake lever . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
5 Assembly overview: Brake pedal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86
5.1 Assembly overview: Brake pedal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86
6 Assembly overview: Brake pedal, Audi S4/S6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92
6.1 Assembly overview: Brake pedal, Audi S4/S6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92
47 - Brakes, Brake hydraulics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
1 Pressurised leak test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
1.1 Pressurised leak test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
2 Servicing Teves/Ate front brake calipers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
2.1 Servicing Teves/Ate front brake calipers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
2.2 Removing and installing piston for front brake caliper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
3 Servicing front brake caliper, two-piston brake caliper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105
3.1 Servicing front brake caliper, two-piston brake caliper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105
3.2 Removing and installing piston for front brake caliper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108
4 Servicing rear brake caliper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
4.1 Servicing rear brake caliper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
4.2 Removing and installing rear brake caliper piston . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114
5 Checking and adjusting brake pressure regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117
5.1 Checking and adjusting brake pressure regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117
5.2 Vehicles with front-wheel drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .117
5.3 Vehicles with four-wheel drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118
6 Checking brake pressure reducer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
6.1 Checking brake pressure reducer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
7 Bleeding braking system, vehicles with and without ABS . . . . . . . . . . . . . . . . . . . . . . . . . .121
7.1 Bleeding braking system, vehicles with and without ABS . . . . . . . . . . . . . . . . . . . . . . . . . .121
7.2 Bleeding brake system with brake filling and bleeding appliance V.A.G 1869 . . . . . . . . . . . .121
7.3 Brake fluid: changing (every 24 months) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
8 Assembly overview: Vacuum-type brake servo/brake master cylinder . . . . . . . . . . . . . . . .127
8.1 Assembly overview: Vacuum-type brake servo/brake master cylinder . . . . . . . . . . . . . . . .127
8.2 Removing and installing brake servo with brake master cylinder . . . . . . . . . . . . . . . . . . . . . .135
9 Assembly overview: Hydraulic brake servo/brake master cylinder . . . . . . . . . . . . . . . . . . . .137
9.1 Assembly overview: Hydraulic brake servo/brake master cylinder . . . . . . . . . . . . . . . . . . . .137
10 Removing and installing pressure reservoir for hydraulic brake servo . . . . . . . . . . . . . . . . . .143
10.1 Removing and installing pressure reservoir for hydraulic brake servo . . . . . . . . . . . . . . . . . .143
10.2 Checking operating pressure of hydraulic brake servo system . . . . . . . . . . . . . . . . . . . . . .148
10.3 Checking charge pressure of pressure reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150
10.4 Checking pressure relief valve of pressure reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150
10.5 Checking non-return valve of pressure reservoir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151
Audi 100 1991 ➤
iiContents

00 - Technical data
1 - Technical data
1.1 - Technical data
1.2 - Brakes
Front brakes
Brake calipers Teves Internal Double piston
up to 06.96
Double piston
as of 06.96
Front brake discs ømm 288 310/312 314 323
Front brake disc, piston diameter mm 57 60 42.8 42.8
Thickness of internally ventilated brake disc mm 25 25 30 30
Brake disc wear limit mm 23 23 28 28
Thickness of unventilated brake disc mm 15 - - -
Brake disc wear limit mm 13 - - -
Brake pad thickness mm 14 12 14 14
Rear-wheel brake (disc)
Rear brake calipers Lucas
Rear brake caliper, piston diameter mm 43
Brake disc; ventilated ømm 269
Brake disc thickness, ventilated mm 20
Brake disc wear limit, ventilated mm 18
Brake disc, non-ventilated ømm 245
Brake disc thickness, non-ventilated mm 10
Brake disc wear limit, non-ventilated mm 8
Brake pad thickness mm 12
Brake pad wear limit mm 2
Rear brake (drum)
Brake drum, rear ømm 230
Wheel-brake cylinder ømm 20.64
Brake pad thickness mm 5
Brake pad, width mm 40
Brake pad wear limit mm 2.5
Audi 100 1991 ➤
1.1 - Technical data 1

1 - Safety precautions and general servicing information
1.1 - Safety precautions and general servicing information
Warning!
The anti-lock brake system is basically maintenance-free.
Testing, assembly and service work is only to be performed by specially trained personnel.
Failure to observe the points described in this Workshop Manual may result in damage to the system and could
make the vehicle unsafe.
◆ Before servicing anti-lock brake system, establish cause of damage by means of self-diagnosis.
◆ Check encoding if a new hydraulic control unit, is fitted.
=> Running Gear Self-Diagnosis; Repair Group 01
◆ Switch off the ignition before removing and installing components. If the vehicle is equipped with a coded
radio, obtain the security code before disconnecting the earthing strap of the battery.
◆ Observe the relevant safety precautions and information when handling brake fluid.
=> Special Information; Running Gear No. 21
◆ If hydraulic system has to be opened, braking system is to be bled on completion of work (e.g. with V.A.G
1869) => Page 121 .
◆ During the concluding road test, ensure that an ABS-controlled brake application is carried out at least once
(can be felt from the pulsing of the brake pedal).
◆ Absolute cleanliness is required when working on the anti lock brake system, and it is not permitted to use
any products which contain mineral oil, such as oil, grease etc.
◆ Thoroughly clean all connection points and surrounding areas before loosening them, but do not use ag‐
gressive cleaning agents such as brake cleaner, petrol, thinners or similar.
◆ Place removed parts on a clean surface and cover.
◆ Carefully cover or seal over components if repairs cannot be carried out immediately. (Use plugs,- repair
set H0 698 311 A)
◆ Use lint-free cloths.
◆ Only remove replacement parts from packaging immediately prior to installation.
◆ Only use genuine packed parts.
◆ When the system is open do not work with compressed air and do not move the vehicle.
◆ Ensure that no brake fluid flows into the electrical connectors.
◆ When carrying out spray painting work, the electronic control unit may be exposed for short periods to a
maximum temperature of 95 oCand for longer periods (about 2 hours) to a maximum temperature of 85oC.
◆ Before carrying out welding work with electric welding equipment
=> General notes, Body Repairs, Safety Precautions
Audi 100 1991 ➤

1.2 - High- and low pressure test
Special tools, testers and workshop equipment required
◆ V.A.G 1310 A Braking system tester
Test requirements:
Make sure that the brake system (hydraulic unit, brake hoses, brake pipes and brake calipers) works properly
and is free of leaks.
High pressure test:
- Remove bleeder screw at one of the front brake calipers. Connect pressure gauge of V.A.G 1310 A and
bleed system.
- Insert brake pedal depressor between brake pedal and driver's seat. Apply pressure to brake pedal until the
gauge indicates a pressure of 50 bar. The pressure must not drop by more than 4 bar during the test period
of 45 seconds. Replace brake master if drop in pressure exceeds the above figure.
Low pressure test:
- Move the brake pedal depressor back until the pressure gauge indicates a pressure of 6 bar.
- The pressure must not drop by more than 1 barduring the test duration of 3 minutes.
Replace hydraulic unit if drop in pressure exceeds the above figure.
Audi 100 1991 ➤
1.2 - High- and low pressure test 3

2 - Removing and installing components of ABS system on front axle
2.1 - Removing and installing components of ABS system on front axle
1 Hexagon bolt
◆ Renew each time after removing
◆ 190 Nm and turn 180o further
Vehicle must be standing on the ground when tightening this bolt.
◆ Switched from hexagon head to hexagon socket. Mixed combinations permitted
2 Wheel bearing housing
3 Clamping sleeve
◆ Identical part on left and right
◆ Grease all round with copper paste before inserting in wheel bearing housing
◆ Press home in wheel bearing housing.
Audi 100 1991 ➤

4 Speed sensor
◆ Removing and installing
=> Page 6
◆ Plug connection for speed sensor =>Page 6
5 Drive shaft with rotor
◆ Inspect rotor for signs of dirt and damage => Page 11
◆ Replace outer CV joint with rotor if rotor is damaged.
=> Audi 100 1991; Running gear, Front and four-wheel drive; Rep.- Gr. 40; Removing and installing drive shaft
◆ Outer CV joint is supplied as a replacement part with the rotor.
6 Bracket
7 Hexagon bolt, 10 Nm
Audi 100 1991 ➤
2.1 - Removing and installing components of ABS system on front axle 5

2.2 - Removing and installing speed sensor
Removing
- Switch off ignition.
- Loosen wheel bolts.
- Jack up vehicle.
- Remove wheel.
- -> Unclip speed sensor wiring from retainers -arrow-.
- Detach connector of speed sensor wiring.
- Pull ABS speed sensor from wheel bearing housing.
Installing
- Renew clamping sleeve (=> Page 4 -Item 3 ).
- Push speed sensor into wheel bearing housing by hand.
- Route speed sensor cable back in original position - see removal.
- Connect speed sensor wiring and press into retainers.
- Fit wheel and tighten to 120 Nm.
- Turn steering to full left lock and full right lock and check clearance of speed sensor wiring.
2.3 - Checking rotor
- Jack up vehicle.
- Remove wheel.
- Pull speed sensor out of wheel bearing housing.
- Inspect rotor for signs of damage or dirt.
- If the rotor is damaged or dirty remove the drive shaft. In the event of damage, replace outer CV joint together
with rotor.
◆ The outer CV joint is supplied as a replacement part with the rotor.
Audi 100 1991 ➤

3 - Removing and installing components of ABS system on rear axle, FWD
models
3.1 - Removing and installing components of ABS system on rear axle, FWD models
Special tools, testers and workshop equipment required
◆ VW 401 Thrust plate
◆ VW 407 Thrust tool
◆ 32-119 Tube
◆ 2050 Thrust piece
◆ V.A.G 1331 Torque wrench
Audi 100 1991 ➤
3.1 - Removing and installing components of ABS system on rear axle, FWD models 7

1 Axle beam
◆ Since MY `97, brake pressure regulators have been fitted at axle beam to reduce brake pressure =>
Fig. 1
2 Hexagon nut 10 Nm
3 Speed sensor
=> Page 10
◆ Release plug connection of wheel speed sensor cable and separate. Unclip speed sensor wiring
4 Clamping sleeve
◆ Press home in wheel bearing housing
Audi 100 1991 ➤

5 Holder for speed sensor
6 Hexagon nut 10 Nm
7 Hexagon socket head bolt,
30 Nm
8 Rotor
◆ Pressing in => Fig. 2
9 Wheel hub
Audi 100 1991 ➤
3.1 - Removing and installing components of ABS system on rear axle, FWD models 9

-> Fig.1 Brake pressure regulator at rear axle as of MY' 97
Since MY' 97, brake pressure regulators have been fitted at the rear axle to reduce brake pressure.
Replacement parts are only available as a set with part no. 4A0 698 401 A.
a - Brake pressure regulator
Note:
◆ When fitting, pay attention to correct installation position and direction of flow -arrow- of brake pressure
regulator.
◆ The flow direction arrow faces away from the direction of travel.
-> Fig.2 Pressing in rotor
- Removing and installing wheel hub
Removing
- Lift rear seat out of its catches.
- Jack up vehicle.
- Remove wheel.
- Unclip speed sensor wiring from retainers.
- Pull speed sensor out of axle beam.
Audi 100 1991 ➤

Installing
- Renew clamping sleeve (=> Page 8 -Item 4 ).
- Jack up vehicle.
- Remove wheel.
- Remove wheel hub if rotor is damaged
- Press in rotor =>Fig. 10 .
Audi 100 1991 ➤
3.2 - Removing and installing speed sensor 11

4 - Removing and installing componpents of ABS system on rear axle, 4WD
models
4.1 - Removing and installing componpents of ABS system on rear axle, 4WD models
1 Drive shaft with rotor
◆ Inspect rotor for signs of dirt and damage => Page 15
◆ If rotor is damaged, replace outer CV joint => Page 15
◆ Outer CV joint is supplied as replacement part with rotor
2 Bracket
3 Wishbone
4 Washer
5 Hexagon nut 10 Nm
Audi 100 1991 ➤

6 Holder for speed sensor
7 Speed sensor
◆ Clean inside surface of hole before inserting sensor
◆ Renewing => Page 14
8 Clamping sleeve
◆ Press home in wheel bearing housing
9 Self-locking nut, 90 Nm
Audi 100 1991 ➤
4.1 - Removing and installing componpents of ABS system on rear axle, 4WD models
13

10 Hexagon bolt
◆ 190 Nm and turn 180o further
Vehicle must be standing on the ground when tightening this bolt
◆ Switched from hexagon head to hexagon socket. Mixed combinations permitted
11 Suspension strut
12 Wheel bearing housing with wheel hub
Removing
- Jack up vehicle.
- Remove wheel.
- Unclip speed sensor wiring from retainers.
Audi 100 1991 ➤

Installing
- Renew clamping sleeve (=> Page 45-17 -Item 8).
- Jack up vehicle.
- Remove wheel.
- If the rotor is damaged or dirty remove the drive shaft. In the event of damage, replace outer CV joint together
with rotor.
◆ The outer CV joint is supplied as a replacement part with the rotor.
5 - Anti-lock brake system (ABS)
5.1 - Anti-lock brake system (ABS)
Observe safety precautions => Page 2
Warning!
Audi 100 1991 ➤
4.2 - Removing and installing speed sensor 15

5.2 - Hydraulic unit and brake pipes
The tightening torque of the brake pipes is 15 Nm.
1 Brake pipe
◆ Hydraulic unit to rear right brake caliper
2 Brake pipe
◆ Hydraulic unit to rear left brake caliper
3 Brake pipe
◆ Hydraulic unit to front right brake caliper
4 Brake master cylinder and brake servo
5 Brake pipes
◆ Brake master cylinder to hydraulic unit
6 Bracket for hydraulic unit
Audi 100 1991 ➤

7 Cover
8 Brake pipe
◆ Hydraulic unit to front left brake caliper
9 ABS-wiring harness
10 Relay for solenoid valves
11 Relay for return pump
12 ABS hydraulic unit
◆ No repair work may be carried out on the hydraulic unit, with the exception of replacing both relays .
Never unfasten bolted joints
◆ If necessary, replace hydraulic unit only as a complete assembly.
◆ Replacement hydraulic units are supplied pre-bled
Audi 100 1991 ➤
5.2 - Hydraulic unit and brake pipes 17

◆ Removing and installing the hydraulic unit
- Disconnect earthing strap from battery
- Seal the brake lines and connections immediately with dummy plugs
- If the hydraulic unit is replaced, bolt the new hydraulic unit onto the bracket-Item 6 -. Remove the dummy
plugs from the brake line connections. The brake lines should be connected in accordance with the
designations on the hydraulic unit
- Bleed brake system => Page 121
- Carry out high- and low-pressure test => Page 3
- Perform electrical test
Audi 100 1991 ➤

13 Earth wire
◆ Ensure good contact
14 Hexagon nut 10 Nm
15 Washer
16 Toothed lock washer
18 Bush
19 Buffer
Audi 100 1991 ➤

5.3 - Removing and installing ABS control unit
Location:
On left below rear seat
- -> Remove both retaining bolts -arrows-
- -> Release connector -see arrow- and separate from control unit -J104.
-> Removing and installing combined relay
Location:
Behind A-pillar-trim at bottom left in auxiliary relay carrier (6-position), relay position 4
- Remove storage compartment for driver`s side.
Audi 100 1991 ➤

- Remove A-pillar-trim.
Combined relay was discontinued as of 07.92.
-> Removing and installing longitudinal acceleration switch
Location:
- Arrow -a- indicates direction of travel.
Longitudinal acceleration switch was discontinued as of 07.92.
6 - Anti-lock brake system (ABS) with electronic differential lock
6.1 - Anti-lock brake system (ABS) with electronic differential lock
Warning!
Audi 100 1991 ➤
5.3 - Removing and installing ABS control unit 21

The tightening torque of the brake pipe is 15 Nm.
1 Suction pipe
◆ Hydraulic unit to brake fluid reservoir
2 Bleed screw
◆ Open to bleed suction pipe
3 Brake pipe
4 Brake pipe
◆ Hydraulic unit to rear right brake caliper
Audi 100 1991 ➤

5 Brake pipe
◆ If necessary, replace hydraulic unit only as a complete assembly
7 Brake pipe
◆ Brake master cylinder/push rod piston circuit to hydraulic unit
8 Brake pipe
◆ Hydraulic unit to rear left brake caliper
Audi 100 1991 ➤

9 Brake pipe
◆ Brake master cylinder/floating piston circuit to hydraulic unit
10 Brake master cylinder
◆ ø 23.81 mm
11 Brake fluid reservoir with float-type indicator
◆ Fill brake fluid up to "max" mark
◆ Connections provided on side for hydraulic clutch controls and EDL-suction pipe
◆ Refer to label on reservoir before topping up brake fluid
◆ Brake fluid: Total quantity approx. 0.6 1 in braking system
12 Angle hose
13 Hose clamp
Audi 100 1991 ➤

7 - Anti-lock brake system (ABS)
7.1 - Anti-lock brake system (ABS)
7.2 - ABS with electronic differential lock (ABS/EDL), ABS/EDL with traction control system
(TCS)
Warning!
Audi 100 1991 ➤
7.1 - Anti-lock brake system (ABS) 25

1 Brake pipe
2 Brake pipe
3 Brake master cylinder and pneumatic brake servo
◆ Audi S4/S6- models feature a hydraulic brake servo => Page 137
4 Brake pipe
5 Brake pipe
◆ Hydraulic unit to rear axle
6 Brake pipe
7 Cover
◆ Fit carefully and secure
◆ Also used for attachment of ABS wiring harness
◆ As of chassis no. PN 039 805, valve relay is provided with an electronic cut-out
9 ABS-wiring harness
Audi 100 1991 ➤

Audi 100 1991 ➤

- If the hydraulic unit is replaced, bolt the new hydraulic unit onto the bracket-Item 19 -. Remove the
dummy plugs from the brake line connections. The brake lines should be connected in accordance with
the designations on the hydraulic unit
- The tightening torque of the brake pipe is 15 Nm.
12 Earth wire
Audi 100 1991 ➤

14 Washer
16 Buffer
17 Bush
Audi 100 1991 ➤

7.4 - Removing and installing control unit for ABS/EDL or TCS
Location:
- -> Remove both retaining bolts -arrows-
- -> Release connector -see arrow- and separate from control unit -J104.
-> Removing and installing combined relay
Location:
Behind A-pillar-trim at bottom left in auxiliary relay carrier (6-position), relay position 4
- Remove storage compartment for driver's side.
Audi 100 1991 ➤

- Remove A-pillar-trim.
Combined relay was discontinued as of 07.92.
-> Removing and installing longitudinal acceleration switch
Location:
- Arrow -a- indicates direction of travel.
Longitudinal acceleration switch was discontinued as of 07.92.
8 - Bosch 5.0 Anti-lock brake system (ABS) as of MY `95 (chassis no. 4ASN ...)
8.1 - Bosch 5.0 Anti-lock brake system (ABS) as of MY `95 (chassis no. 4ASN ...)
8.2 - ABS with electronic differential lock (ABS/EDL), ABS/EDL with traction control system
(TCS)
Warning!
Introduction of the Bosch 5.0 ABS/EDL/TCS was accompanied by modification of the central valves of the
master brake cylinder. This cannot be recognised from the external appearance. Using the wrong valves could
impair vehicle safety. Observe part no.
Audi 100 1991 ➤
7.4 - Removing and installing control unit for ABS/EDL or TCS 31

1 Brake master cylinder and brake servo
2 Brake pipe
◆ Screw connection at brake master cylinder: M12x1
◆ Screw connection at hydraulic unit: M12x1
3 Brake pipe
◆ Screw connection at brake master cylinder: M12x1
◆ Screw connection at hydraulic unit: M12x1
Audi 100 1991 ➤

4 Connector, ABS wiring harness
◆ Release and detach
◆ The connector is part of the ABS wiring harness. Note that there are different versions for FWD and 4WD
models.
◆ Note dissimilar fixing points => Fig. 1 , 2 and 3
◆ Hydraulic unit/pipe connections/rear => Fig. 1 , 2 and 3
Audi 100 1991 ➤

- If the hydraulic unit is replaced, bolt the new hydraulic unit onto the bracket -Item 15 - -.Remove the
dummy plugs from the brake line connections. The brake lines should be connected in accordance with
the designations on the hydraulic unit
- The tightening torque of the brake pipe is 15 Nm.
Audi 100 1991 ➤

8 Cover
9 Bolt, 5 Nm
10 Stud, 15 Nm
11 Buffer
12 Bush
Audi 100 1991 ➤

14 Earth wire
Note:
Items - 16 -, - 17 -, - 18 - and - 19 - are only fitted on vehicles with auxiliary heater.
16 Auxiliary heater water pipe
17 Washer
18 Self-locking nut
19 Bracket
Audi 100 1991 ➤

22 Earth wire
23 Stud, 8 Nm
-> Fig.1 Brake pipe connections at hydraulic unit
1 - Hydraulic unit - brake master cylinder (push rod piston circuit)
2 - Hydraulic unit-rear right brake caliper
3 - Hydraulic unit -front left brake caliper
Audi 100 1991 ➤

4 - Hydraulic unit-brake master cylinder (floating piston circuit)
5 - Hydraulic unit- rear left brake caliper
6 - Hydraulic unit- front right brake caliper
-> Fig.2 Brake pipe connections at hydraulic unit, pressure control
For models with 4WD and ABS/EDL- pressure control (up to 05 95):
Two pressure dampers are screwed into the hydraulic unit -arrows-on vehicles with 4WD and EDL pressure
control.
The dampers are designed to smooth pressure peaks in the brake pipes and reduce control noises.
Counterhold at the hexagon of the pressure dampers when unfastening the brake pipes.
1 - Hydraulic unit-brake master cylinder (push rod piston circuit)
3 - Hydraulic unit-front left brake caliper
5 - Hydraulic unit- rear left brake caliper
6 - Hydraulic unit- front right brake caliper
-> Fig.3 Hydraulic unit for ABS/EDL-4WD, suction control.
The pressure dampers are not fitted to vehicles with 4WD and EDL suction control (05.95 onwards) => Fig. 2
The EDL suction control minimises control noises.
The working range of the pressure limiting valve in the hydraulic unit is raised from 90±25 bar to 170±25 bar.
1 - Hydraulic unit-brake master cylinder (push rod piston circuit)
3 - Hydraulic unit -front left brake caliper
Audi 100 1991 ➤

5 - Hydraulic unit rear left brake caliper:
6 - Hydraulic unit- front right brake caliper:
8.4 - Removing and installing control unit for ABS/EDL or TCS
Location:
- -> Release connector -lower arrow- and separate from control unit -J104.
- Remove both retaining bolts -upper arrows-
Install in reverse order
Audi 100 1991 ➤

1 - Servicing front brakes
1.1 - Servicing front brakes
1.2 - Servicing Teves/Ate front brakes
Note:
◆ Always install the complete repair kit.
◆ After replacing brake pads, depress brake pedal firmly several times with vehicle stationary so that the brake
pads are properly seated in their normal operating position.
Audi 100 1991 ➤

◆ To draw off brake fluid from the reservoir, use a bleeder bottle which is used only for brake fluid. Brake fluid
is poisonous and must on no account be sucked out by mouth using a hose!
◆ Brakes can be checked on all commercially available brake test stands, provided that the driving speed of
the two driving rollers of the test stand does not exceed 5.5 km/h.
◆ The tightening torque of the brake pipe is 15 Nm.
1 Guide pin, 25 Nm
2 Trim cap
◆ Take off
◆ With hook at bottom for routing wiring of brake pad wear indicator
3 Connector
◆ Take out of bracket at brake caliper on brake pad replacement
Audi 100 1991 ➤
1.2 - Servicing Teves/Ate front brakes 41

5 Bracket
◆ Bolt to brake caliper housing
◆ Insert connector for brake pad wear indicator
6 Brake hose
◆ Do not disconnect brake hose when changing brake pads
7 Brake pipe, 15 Nm
◆ Screw into brake caliper housing
◆ Screw into brake hose, counterholding at hexagon on brake hose.
8 Ribbed bolt, 125 Nm
◆ Clean ribbings if reusing
9 Brake backplate
◆ Bolt to wheel bearing housing
Audi 100 1991 ➤

10 Brake pads
◆ Always replace on both sides of the car
◆ With wear indicator
- Once wear limit is reached, warning light in dash panel insert comes on
◆ The outer brake pads are provided with an adhesive sheet on the backing plate of the pad. Remove the
protective sheet before inserting pads.
◆ Thickness 14 mm
◆ check thickness
=> Audi 100 1991; Maintenance
◆ Wear limit: 7 mm (including backplate)
◆ Removing and installing => Page 46
Always clean the brake calipers (no grease) before inserting new brake pads. Make sure that all adhesive sheet
residue on the contact surfaces of the outer brake pad is removed.
Audi 100 1991 ➤

11 Retention spring
◆ Insert into both holes of the brake caliper housing
Note:
After inserting the retaining spring into both holes, it has to be pressed below the brake carrier. If incorrectly
installed, it is not possible to adjust the wear of the outer pad and the pedal travel will be increased as a result.
Audi 100 1991 ➤

12 Brake disc
◆ Remove brake caliper prior to removing
◆ Always dress evenly, on both sides, starting from thickness when new
◆ Internally ventilated brake disc: ø 288 mm
◆ Brake disc thickness: 25 mm
◆ Wear limit: 23 mm
◆ Non-ventilated brake disc: ø 288 mm
13 Brake caliper housing
◆ Unscrew from brake carrier to replace brake pads
◆ Servicing brake calipers => Page 99
Audi 100 1991 ➤

1.3 - Removing and installing brake pads
Special tools and workshop equipment required
Removing
Note:
Mark brake pads to be reused on removal. Reinstall in their original position to prevent uneven braking!
- Jack up vehicle.
- Remove wheel.
- -> Detach connector; to do so, press spring -left arrow- and pull off plug.
- -> Use screwdriver to carefully lift tab slightly on bottom part of plug, then turn through 90oanti-clockwiseor
clockwiseand remove from bracket.
- Pull wire for brake-pad wear indicator out of cap.
- Remove protective caps.
Audi 100 1991 ➤

- -> Lever off brake pad retaining spring from brake caliper housing with a screwdriver and remove.
- -> Unscrew both guide pins and remove from brake caliper.
- Take off the brake caliper housing and lay to one side so that the weight of the brake caliper does not pull
on or damage the brake hose.
- Take brake pad out of brake caliper housing or from brake carrier.
Installing
- -> Pressing piston back.
Note:
Before inserting new brake pads, press piston back into the cylinder with resetting tool. Before pressing the
piston back, draw off brake fluid from the reservoir with a bleeder bottle. Otherwise brake fluid - which was used
to top up the brake fluid reservoir-, may run outs and cause damage.
Audi 100 1991 ➤
1.3 - Removing and installing brake pads 47

Warning!
Brake fluid is poisonous and must on no account be siphoned orally through a hose.
- -> Insert brake pad with wire for wear indicator in brake caliper housing.
- Pull off protective sheet on backing plate of outer brake pad.
- Fit outer brake pad to brake carrier.
- -> Secure brake caliper housing to brake carrier with both guide pins to 25 Nm.
- Insert bottom part of plug of brake pad wear indicator in bracket at brake caliper.
- Fit both protective caps.
- Position wire for brake-pad wear indicator in cap.
- Connect connector.
- Insert retaining spring into brake caliper housing.
Note:
◆ After inserting the retaining spring into both holes, it has to be pressed below the brake carrier. If incorrectly
installed, it is not possible to adjust the wear of the outer pad and the pedal travel will be increased as a
result.
After replacing the brake pads, depress brake pedal firmly several times with the vehicle stationary, so that the
brake pads are properly seated in their normal operating position.
- Check brake fluid level and top up if necessary.
Audi 100 1991 ➤

1.4 - Servicing front brake, internal caliper disc brake
Audi S4
Note:
1 Wheel bearing housing
3 Cover plate
5 Brake disc
◆ Internally ventilated brake disc: ø 310/312 mm
Audi 100 1991 ➤
1.4 - Servicing front brake, internal caliper disc brake 49

6 Bolt, 4 Nm
◆ Servicing is not envisaged
◆ Only replace as complete unit
8 Wire for brake pad wear indicator
9 Brake pads
◆ always replace on both sides of the car
◆ with wear indicator
- Once wear limit is reached, warning light in dash panel insert comes on.
◆ Thickness 12 mm
◆ check thickness
◆ Wear limit: 7 mm including backplate
Audi 100 1991 ➤

Note:
Always clean the brake calipers (no grease) before inserting new brake pads. Make sure that all adhesive sheet
residue on the contact surfaces of the outer brake pad is removed.
10 Pad retaining spring
◆ Replace
11 Cable tie
◆ Replace
◆ Attach wire for brake pad wear indicator to bracket Item.- 14 - .
12 Connector
14 Bracket
15 Brake hose
16 Retention spring
17 Brake pipe, 15 Nm
◆ Screw into brake caliper housing
◆ Screw into brake hose, counterholding at hexagon on brake hose.
◆ Clean ribbing if reusing
Audi 100 1991 ➤
1.4 - Servicing front brake, internal caliper disc brake 51

Removing
Note:
- Jack up vehicle.
- Remove wheel.
- -> Detach connector; to do so, press spring and pull off plug.
Audi 100 1991 ➤

- Cut through cable tie at bracket.
- -> Lever off brake pad retaining spring from brake caliper housing with a screwdriver and remove.
- -> Pressing piston back.
Audi 100 1991 ➤

- -> Firmly press brake caliper housing in direction of arrow as far as it will go.
- Take piston-end brake pad out of brake caliper housing.
- -> Screw out bolt for brake disc -arrow- tilt brake disc outwards and detach.
- Take outer brake pad out of brake caliper housing.
- -> Pull wire for brake pad wear indicator off brake pad -arrow-.
Note:
Damaged wires can be replaced after disconnection at coupling.
Thoroughly clean brake caliper housing before installing new brake pads.
In particular, watch for residual adhesive sheet from the outer brake pads.
Installing
- Attach wire for brake pad wear indicator to brake pad.
- Insert brake pad with wire for wear indicator.
Note:
Retaining spring of brake pad must be heard to engage in brake caliper.
- Attach new cable tie to bracket.
Audi 100 1991 ➤

- Insert brake disc.
- -> Screw in bolt for brake disc -arrow-.
- Install piston-end brake pad in brake caliper housing.
- Insert retaining spring into brake caliper housing.
- Pull protective sheet off backplates of outer brake pads.
Note:
◆ Firmly depress brake pedal several times after each change of brake pads, so that the brake pads are
properly seated in their normal operating position.
- Fit wheels to 120 Nm.
1.6 - Servicing front brakes, two-piston brake
Audi S4/S6, Audi S4.2, Audi S6 Plus
Note:
Audi 100 1991 ➤

1 Torx bolts, 25 Nm
◆ Always replace
◆ Remove and insert using commercially available Torx socket (e.g. Hazet T40)
◆ Included in brake pad repair set
Audi 100 1991 ➤

2 Brake disc
◆ Ensure adequate wear reserve
◆ Internally ventilated brake disc: ø 314 mm
◆ Internally ventilated brake disc on Audi S6 Plus (240 KW) as of 06.96: ø 323 mm
3 Brake calipers
◆ If assembly work is required, do not leave caliper hanging from brake hose but secure it to bodywork
with wire
◆ Adapted to brake disc dia. of ø 323 mm on Audi S6 Plus (240 KW) as of 06.96
Audi 100 1991 ➤
1.6 - Servicing front brakes, two-piston brake 57

◆ Clean ribbing if reusing
5 Brake pipe, 15 Nm
6 Retention spring
7 Bracket
8 Brake hose
◆ Do not unscrew to replace brake pads
10 Connector
Audi 100 1991 ➤

11 Cable holder
◆ Insert cable for brake pad wear indicator into cable holder
12 Brake pads
◆ Different designs on left and right
◆ With wear indicator
- Once wear limit is reached, warning light in dash panel insert comes on.
◆ Pad thickness: 14 mm
◆ check thickness
◆ Wear limit: 7 mm including backplate
Audi 100 1991 ➤
1.6 - Servicing front brakes, two-piston brake 59

Removing
Note:
- Jack up vehicle.
- Remove wheels.
- -> Secure brake disc with a wheel bolt.
- Unscrew both Torx bolts for the outer brake pads.
Audi 100 1991 ➤

Note:
Before pressing back the piston, extract brake fluid from the brake fluid reservoir with a bleeder bottle. Otherwise
brake fluid - which was used to top up the brake fluid reservoir-, may run outs and cause damage.
Warning!
- -> Press piston back into brake caliper housing.
- To do so, insert sliding caliper with screwdriver as shown and press firmly outwards.
- First remove outer brake pad, to do so, use screwdriver to press brake pads off brake caliper.
- -> Detach connector; to do so, press spring and pull off plug.
- Pull wire for brake pad wear indicator out of bracket at brake caliper.
Audi 100 1991 ➤

- -> Firmly press floating caliper in direction of arrow as far as it will go.
- Use screwdriver to carefully press brake pads out of piston and remove from brake caliper housing.
Note:
Thoroughly clean brake caliper housing before installing new brake pads.
In particular, watch for residual adhesive sheet from the outer brake pads.
Installing
- -> Insert brake pad with wire for wear indicator into upper piston.
Note:
Take care not to damage protective caps when inserting brake pads.
- -> Insert lower brake pad in piston.
- Clip wire for brake pad wear indicator into bracket at brake caliper.
Audi 100 1991 ➤

- -> Press floating caliper outwards as far as it will go.
- Pull protective sheet off backplates of outer brake pads.
Note:
◆ The repair kit includes four self locking Torx bolts which must be installed in all cases.
- -> Screw the Torx bolts from the repair set into the floating caliper and fix the brake pads in position.
◆ Tightening torque: 25 Nm
- Unscrew wheel bolt from wheel hub.
Note:
When fitting on the wheels, make sure that the rim flange is not mounted onto the brake caliper.
This could otherwise press the brake pads out of their guides.
Audi 100 1991 ➤

2 - Servicing rear wheel brake (disc brake)
2.1 - Servicing rear wheel brake (disc brake)
Rear brakes with automatic adjustment
Note:
Audi 100 1991 ➤

◆ Brakes can be checked on any commercially available brake test stand, provided that the driving speed of
the two driving rollers of the test stand is not more than 5.5 km/h.
1 Hexagon bolt, Self-locking , 35 Nm
◆ Always replace
◆ When loosening and tightening counter hold on guide pin
◆ Servicing brake calipers => Page 110
Audi 100 1991 ➤
2.1 - Servicing rear wheel brake (disc brake) 65

3 Brake pads
◆ Thickness 12 mm
◆ Checking thickness:
◆ Wear limit: 7 mm (including back plate)
4 Brake carrier with guide pin and protective cap
◆ Supplied as replacement part assembled with sufficient quantities of grease on guide pins
◆ If protective caps or guide pins are damaged, install repair kit. Use grease sachet supplied to lubricate
guide pins.
Audi 100 1991 ➤

5 Brake disc
◆ Always dress evenly, on both sides, starting from thickness when new
◆ Brake disc diameter
- ventilated: 269 mm
- non-ventilated: 245 mm
◆ Brake disc thickness
- ventilated: 20 mm
- non-ventilated 10 mm
◆ Wear limit
- ventilated: 18 mm
- non-ventilated 8 mm
6 Cheese-head bolt, 60 Nm
Audi 100 1991 ➤
2.1 - Servicing rear wheel brake (disc brake) 67

◆ 3272 Resetting and removing tool
Removing
Note:
- Jack up vehicle.
- Remove wheels.
- -> Remove bolts from brake caliper housing, counterholding on guide pins.
- Remove brake pads.
Audi 100 1991 ➤

Installing
Before inserting new brake pads, press piston back into the cylinder with resetting tool. Before pressing the
piston back, draw off brake fluid from the reservoir with a bleeder bottle. Otherwise brake fluid which was used
to top up the brake fluid reservoir, may run outs and cause damage.
Warning!
- -> Screw piston by turning knurled wheel of special tool 3272 clockwise.
Note:
◆ Fit special tool 3272 so that the collar of the tool is seated against the brake carrier.
◆ If the piston is pushed back with a piston resetting tool the automatic adjustment in the brake caliper will be
destroyed.
- Pull protective foil off outer brake pad backplate.
- -> Insert brake pads.
- Tighten bolts on brake caliper housing, 35 Nm.
Note:
◆ The repair kit includes four self-locking hexagon bolts which must be installed in all cases.
Audi 100 1991 ➤

2.3 - Basic setting of rear wheel brake
Handbrake cable must not be pretensioned when performing basic setting (release handbrake).
Check:
- -> Use screwdriver to alternately press levers for handbrake cable against. . .
- -> . . . stop (see arrow).
If lever of opposite brake caliper is pulled off stop, then handbrake cable is excessively pretensioned.
Note:
For ease of illustration, stop is shown with brake caliper removed.
- -> Slacken off adjusting nut -arrow- for handbrake cable until both levers make contact with stop of brake
caliper.
Audi 100 1991 ➤

Vehicles with pressure regulator
- -> Jam drill bit of at least ø 6 mm dia. between end of spring at bottom and mount.
- Press brake pedal twice.
- Take out drill bit.
- Check whether both wheels can spin freely.
Vehicles with self-levelling suspension
- Stand vehicle on ground.
- Leave engine idling for at least 2 minutes.
- Press brake pedal twice.
- Check whether both wheels can spin freely.
2.4 - Adjusting handbrake
Note:
◆ Due to the automatic rear wheel brake adjustment there is no requirement to adjust the handbrake. Adjust‐
ment is only necessary if the handbrake cables, brake calipers, brake pads and brake discs are renewed.
◆ The foot brake system must have been bled and must be functioning properly.
◆ Handbrake must be adjusted before installing centre console and handbrake trim.
Checking basic setting:
- -> Use screwdriver to alternately press levers for handbrake cable against . . .
Audi 100 1991 ➤
2.3 - Basic setting of rear wheel brake 71

- -> . . . stop (see arrow).
If lever of opposite brake caliper is pulled off stop, then handbrake cable is excessively pretensioned.
Note:
Adjusting:
- Depress brake pedal firmly at least 1*.
- Handbrake lever in release position.
- -> Slacken off adjusting nut -arrow- for handbrake cable until both levers make contact with stop of brake
caliper.
- Tighten nut on connecting rod until both levers at brake calipers clearly move (two mechanics required).
- Depress handbrake firmly at least 3*.
- -> Set adjusting nut on connecting rod such that one lever at one brake caliper just lifts off stop.
- Re-check basic setting => Page 71
Audi 100 1991 ➤

Note:
3 - Servicing rear wheel brake (drum brake)
3.1 - Servicing rear wheel brake (drum brake)
3.2 - Removing and installing rear brake
1 Axle beam
2 Stub axle
3 Brake carrier with brake shoes
◆ reset before removing brake drum
=> Page 76
5 Handbrake cable
◆ Adjusting handbrake
Audi 100 1991 ➤
2.4 - Adjusting handbrake 73

=> Page 81
6 Brake drum
◆ Brake drum diameter, 230 mm
◆ Wear limit 231 mm
◆ Clean carefully, check for wear, damage, dimensional accuracy, damaged wheel bolt threads and perfect
brake contact surface
7 Outer wheel bearing
8 Hexagon nut
◆ Adjusting wheel bearing play
=> Fig. 3
9 Grease cap
◆ Pressing off =>Fig. 1 and 2
◆ Pressing in => Fig. 4
10 Thrust washer
11 Locking ring
12 Split pin
◆ Replace
Audi 100 1991 ➤

-> Fig.1 Pressing off grease cap
- Tap gently to detach grease cap from its seat.
-> Fig.2 Pressing off grease cap
Audi 100 1991 ➤
3.2 - Removing and installing rear brake 75

-> Fig.3 Adjusting wheel bearing play
Note:
It must be possible to move the thrust washer by exerting pressure using a screwdriver (without leverage).
- Secure with locking ring and new split pin.
-> Fig.4 Driving home grease cap
Note:
◆ Always replace damaged grease caps.
◆ Damaged grease caps allow ingress of moisture. Therefore, always use the tool shown.
3.3 - Resetting brake
- -> Insert screwdriver through wheel-bolt tapped hole in brake drum to press up key.
Audi 100 1991 ➤

3.4 - Servicing rear brakes
After performing work on rear brake:
◆ Release handbrake.
◆ Firmly press brake pedal once.
1 Spring plate
◆ To remove, press against compression spring and turn through 90o
2 Spring
3 Brake shoe with lever for handbrake
=>Page 80
◆ Adjusting handbrake=>Page 81
Audi 100 1991 ➤
3.4 - Servicing rear brakes 77

4 Upper return spring
◆ Disengage with spring pincers
5 Lower return spring
◆ Grease contact points with lubricating paste, part- no. G 000 650
6 Tension spring
7 Brake shoe
=>Page 80
◆ Minimum pad thickness 2.5 mm
◆ check thickness
8 Cap
◆ Remove to check brake pad thickness
9 Spring pin
Audi 100 1991 ➤

10 Brake backplate
11 Hexagon socket-head bolt,
10 Nm
12 Wheel-brake cylinder
◆ Leak test
=> Fig. 1
13 Key
◆ To remove and install brake drum, press upwards through wheel-bolt hole=> Page 76
14 Push rod
◆ Grease contact points with lubricating paste, part- no. G 000 650
15 Locating spring
◆ Disengage with spring pincers
Audi 100 1991 ➤
3.4 - Servicing rear brakes 79

-> Fig.1 Checking wheel-brake cylinder for leaks
- Lift off dust sleeve
- Replace wheel-brake cylinder if brake fluid is found in dust sleeve.
Take care not to damage dust sleeve when lifting off.
3.5 - Removing and installing brake shoes
Removing
- Reset brake => Page 76 .
- Pressing off grease cap => Page 75
- Removing brake drum.
- Removing spring plate.
- Disengage lower return spring.
- Detach brake shoes.
- Disengage handbrake cable.
- Clamp brake shoes in vice.
- -> Remove tension spring for key.
- Removing upper return spring.
Audi 100 1991 ➤

- -> Disengage locating spring.
Installing
- -> Engage locating spring and position brake shoe on push rod.
- Fit key.
- -> Insert brake shoe with brake lever in push rod.
- Engaging upper return spring.
- Engage handbrake cable at brake lever.
- Position brake shoes on pistons of wheel-brake cylinder.
- Insert lower return spring and lift brake shoe onto lower support.
- Engage tension spring for key.
- Insert compression spring with spring plate.
- Install brake drum and insert wheel bearing play Adjusting wheel bearing play => Page 76
- Press foot brake firmly once to set rear brake.
3.6 - Adjusting handbrake
Note:
Due to the automatic rear wheel brake adjustment there is no requirement to adjust the handbrake. Resetting
is only required after replacing handbrake cables, brake carriers or brake pads.
Audi 100 1991 ➤
3.5 - Removing and installing brake shoes 81

- Release handbrake.
- Firmly press brake pedal once.
- Pull on handbrake lever 3 notches.
- -> Tighten adjusting nut -arrow- until both wheels are difficult to turn by hand.
- Release handbrake and check, whether both wheels can spin freely. If necessary, screw back adjusting
nuts slightly.
4 - Handbrake lever - exploded view
4.1 - Handbrake lever - exploded view
Note:
◆ On RHD vehicles, the handbrake lever is fitted flush with the right side of the centre console (flush with left
side on LHD vehicles).
◆ Grease all bearing points prior to assembly with lithium grease, part no. N 052 738 00.
The following applies to both LHD and RHD vehicles.
1 Grip
◆ Slip onto handbrake lever
◆ Press home tab after assembly
Audi 100 1991 ➤

◆ To dismantle, carefully press out tab with screwdriver
2 Bolt
3 Centre console
4 Handbrake lever
=> Page 85
◆ Available as assembly together with connecting rod, ratchet, push button, compression spring and lock‐
ing segment
◆ Locking segment is also available as a separate replacement part
5 Circlip
◆ Replace
◆ Ensure correct positioning
Audi 100 1991 ➤
4.1 - Handbrake lever - exploded view 83

6 Bolt
7 Switch for handbrake controls
8 Mount for handbrake lever
9 Spring
10 Bolt
11 Compensator
◆ Installation position: Viewed in direction of travel, long side faces right
12 Adjusting nut
◆ Adjusting handbrake => Page 71
13 Bellows
◆ Ensure correct positioning
14 Fulcrum pin
◆ For supporting handbrake lever
Audi 100 1991 ➤

4.2 - Removing and installing handbrake lever
Removing
- Removing centre console
- Remove rear exhaust on quattro vehicles.
- Removing centre heat-insulation panels.
- Unscrew adjusting nut from connecting rod.
- Detach compensator.
- Detach bellows.
- -> Disengage circlip -arrow- from pivot pin.
- Press out pivot pin.
- Push handbrake lever slightly to rear and take out.
Install in reverse order.
Pay special attention to the following on installation:
- Insert circlip carefully.
- Insert bellows carefully.
- Ensure stress-free installation of exhaust system.
- Adjust handbrake (brake disc) => Page 71 .
- Adjust handbrake (brake drum) => Page 81 .
Audi 100 1991 ➤
4.2 - Removing and installing handbrake lever 85

5 - Assembly overview: Brake pedal
5.1 - Assembly overview: Brake pedal
Warning!
The brake pedal travel must not be shortened by additional floor coverings.
2 Mounting
◆ Disengage Procon cable on removal
3 Supply hose
◆ Attach to master cylinder
4 Clip
◆ Insert in mounting bracket
Audi 100 1991 ➤

5 Locking clip
◆ Fit onto pin
6 Over-centre spring
=> Fig. 2
7 Locking clip
◆ Attach to shaft of mounting bracket
8 Locking clip
◆ Fit onto pin
9 Cheese head bolts, 20 Nm
◆ Screw master cylinder to pedal bracket
Audi 100 1991 ➤
5.1 - Assembly overview: Brake pedal 87

10 Clutch pedal
◆ Located in position by clutch master cylinder adjustment
◆ Slip onto shaft of mounting bracket
◆ Replacement part supplied with moulded mounting bush which cannot be replaced
11 Cap
12 Rear spring for brake pedal
◆ Installation position: Long arm in mounting bracket and short arm in brake pedal
13 Locking clip
◆ Attach to shaft of mounting bracket
Audi 100 1991 ➤

14 Brake pedal
◆ Slip onto shaft of mounting bracket
◆ Replacement part supplied with moulded mounting bush which cannot be replaced
◆ To remove and install, remove mounting bracket
15 Cap
16 Brake light switch
◆ Adjusting:
- Brake pedal operated
- Press in brake light switch as far as it will go
- Pull back brake pedal as far as it will go
17 Clip
◆ Insert in mounting bracket
Audi 100 1991 ➤
5.1 - Assembly overview: Brake pedal 89

18 Washer
20 Pin
◆ Insert in clutch pedal and master cylinder
21 Fork
22 Lock nut, 50 Nm
23 Master cylinder
◆ Replace in the event of leakage
◆ Adjusting => Fig. 1
Audi 100 1991 ➤

Audi 100 dupa 1991 brake system

Audi 100 dupa 1991 brake system

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